Mobile telephones are ubiquitous in modem societies. Once owned and carried only by the affluent or persons in specialized occupations that both required and supplied them, mobile phones are now owned by the many, and sometimes even by the majority of a given population. And no longer are mobile telephones used by only a small segment of the population, but rather now by people of all ages and walks of life.
There are several reasons for this widespread use of mobile phones. The first and foremost, of course, is technology. The development of a cellular system of organizing radio traffic has made possible the subscribing of thousands of customers in a single metropolitan area. Improved multiplexing and modulation techniques have contributed to the ability to handle vast numbers of customers. Coverage has improved as well; that is, the amount of geographic area in which a mobile-system subscriber is within range of a network antenna. At the same time, the cost of the mobile telephone itself and of a subscription to a mobile communications network have fallen and made mobile phone use affordable. Improved technology has also led to the development of ever-smaller and easier-to-use phones. As such improvements in technology often do, rising mobile-phone popularity led to increasingly large markets, which in turn encouraged further innovation.
When, as in the past, mobile phones were used by only a limited set of users (often referred to as subscribers), designs were austere and functional. As long as the instrument performed its given task, appearance was an unimportant consideration. The first mobile phones were large and bulky, and often kept out of sight unless being used. Such use was often kept to a minimum because wireless calls were expensive. Even where possession of the device served as a sort of status symbol, merely having it was sufficient to convey the presumed air of importance.
As the number of mobile subscribers grew, however, and the cost of air time declined, mobile phones became more visible. It is presently as unusual to venture into public and not see someone using a mobile phone as it was in the past to observe someone's cell-phone call. Not unexpectedly, the demand for aesthetically attractive telephones grew with more common usage. Of course, vastly increased mobile phone sales allowed manufacturers to diversify, where previously the cost of implementing more than one or two basic designs would be unreasonable. Demand for new and varied designs also stems from the fact that many mobile phone owners are young adults and adolescents with different tastes than professional business people.
At the same time, the utility of wireless communications devices has increased. Beyond making and receiving calls, mobile phones and similar devices now have the capability to store a phone directly and log calls. Many also include clocks, calendars, and calculators. Others may be used as electronic organizers, or to play games, or even to download Web pages over a wireless connection to an Internet Service Provider (ISP). In this they emulate modem personal digital assistants (PDAs), which started as simple organizers and have themselves grown in functionality. In fact, there is now great variety among the different types of portable devices that are capable of wireless communication. In light of this variety, the term “mobile station” will for convenience be used herein to refer generally to these and similar devices (whether they perform wireless communications or just some of the other functions).
One feature all of these devices must include, however, is one or more forms of user interface. Most include a visual display screen, usually a liquid-crystal display (LCD). Those used for communicating (or recording) will have a microphone and speaker, or at least a port through which a separate microphone and speaker may be connected. Finally, all, or almost all mobile stations include a keypad. The keypad is a set of external, user-accessible push-buttons or similar mechanisms used to enter information or make the device perform certain functions. There are many different designs for keypads and different buttons that may be included in them. Each button may have more than one function. In a typical device, however, there will be a set of buttons associated with alphanumeric (and a few other) characters. Specialized buttons may be used for scrolling (moving images up and down or sideways in the display), to initiate or terminate a call, or some function that varies with application state. The keyboard buttons are usually not switches themselves, but rather correspond with, and thus operate internally located switches. They are frequently made of an insulating material because the voltages used by mobile stations are so small that there must be no opportunity for a user to contact any electrical components. For manufacturing convenience, all or some of the buttons may be integrally formed along a sheet of (typically) non-conducting material, with individual buttons identified by a raised surface, visible markings, or both. This sheet of buttons is commonly referred to as a keymat.
The keymat is typically made of an elastomeric material so that it is non-conducting, flexible, and resilient. Any given device may have one or more keymats, with each keymat usually, though not necessarily, forming a plurality of keys. Each keymat is captured inside of an exterior housing portion and itself is inaccessible to the user. The exterior housing portion, however, forms one or more openings corresponding to each button, or key, on the keymat, allowing the raised portions of the keymat to protrude toward the device's exterior. The keymat is also supported from the interior side in such a way that the user can, by pressing or otherwise manipulating a key, cause activation of only the desired switch or switches, and so that when the key is released, it and its associated switch return to their resting state. For more detail regarding conventional construction, refer to FIG. 1 and the related descriptive text below.
Enclosed in this typical fashion, however, the keymat contributes only a little to the device's overall appearance. It's functional configuration is well-suited to operating the mobile station, but even if more artistically designed, it does little to impact the ‘look’ of the instrument. It is certainly not easily exchangeable, generally being replaced only by a service technician, and then only when necessary. It cannot ordinarily be used to customize the mobile station's appearance to any significant degree.
Needed is a mobile-station keypad having a keymat that can be conveniently removed and installed so that the user may easily exchange keymats for aesthetic or functional reasons, but at the same time does not detract significantly from the mobile station's normal operation or integrity. The keymat design of the present invention provides just such a solution.